The present technology relates to a separator. Further, the present technology relates to a nonaqueous electrolyte battery having a separator between electrodes, as well as a battery pack, an electronic device, an electric vehicle, a power storage device, and a power system that use this nonaqueous electrolyte battery.
Secondary batteries, such as lithium ion secondary batteries, are used as a power source battery in mobile devices such as a laptop computer, a vehicle power storage battery for hybrid vehicles, battery-powered vehicles and the like, as well as a power storage battery that is combined with a new energy system such as a solar cell, wind power generation and the like.
To increase the capacity of a lithium ion secondary battery even further, it has been proposed to use a material capable of forming an alloy with lithium as a negative electrode active material. For example, an alloy-based negative electrode material that includes an element having a greater theoretical capacity than a carbon material and that is capable of forming an alloy with lithium, such as silicon or tin, has been proposed as such a negative electrode active material (e.g., refer to Patent Literature 1).
Since an alloy-based negative electrode material exhibits very large expansion during charging, there is the problem that deterioration of the electrode, such as damage and fracturing of the electrode, can occur from the pressure due to expansion.
To overcome this problem, a technology has been reported in which the expansion of the alloy-based negative electrode material is absorbed by forming an uneven shape on the separator. For example, in Patent Literature 1, a technology is proposed that absorbs expansion of the negative electrode by forming an uneven shape by an embossing process on a polyolefin microporous film.
Further, in Patent Literature 2, a technology has been proposed for suppressing electrode deterioration caused by expansion and contraction of an electrode by forming voids between a polyolefin microporous film and the electrode. A technology is proposed for forming the voids between the a polyolefin microporous film and the electrode by placing a spacer between the polyolefin microporous film and the electrode, and removing the spacer later.